Cave‐dwelling animals evolve distinct troglomorphic traits, such as loss of eyes, skin pigmentation, and augmentation of senses following long‐term adaptation to perpetual darkness. However, the molecular genetic mechanisms underlying these phenotypic variations remain unclear. In this study, we conducted comparative histology and comparative transcriptomics study of the skin of eightSinocyclocheilusspecies (Cypriniformes: Cyprinidae) that included surface‐ and cave‐dwelling species. We analyzed four surface and four cavefish species by using next‐generation sequencing, and a total of 802,798,907 clean reads were generated and assembled into 505,495,009 transcripts, which contributed to 1,037,334 unigenes. Bioinformatic comparisons revealed 10,629 and 6,442 significantly differentially expressed unigenes between four different surface‐cave fish groups. Further, tens of differentially expressed genes (DEGs) potentially related to skin pigmentation were identified. Most of these DEGs (includingGNAQ,PKA,NRAS, andp38) are downregulated in cavefish species. They are involved in key signaling pathways of pigment synthesis, such as the melanogenesis, Wnt, and MAPK pathways. This trend of downregulation was confirmed through qPCR experiments. This study will deepen our understanding of the formation of troglomorphic traits in cavefishes.

Chikungunya virus (CHIKV) infection causes joint damage and gastrointestinal clinical symptoms, including vomiting and diarrhea, particularly in elderly populations, reflecting the potential role of gut immunity in infection. However, the mechanisms by which CHIKV induces gastrointestinal diseases remain largely unexplored. This study investigated the characteristics of fecal and gut microbiota, gut metabolites, and gut immunity post-infection using multi-omics analysis. The role of gut microbiota was further validated through Oral antibiotic depletion (Abx). Importantly, a systematic comparison of age-dependent differences in gut microbiota composition and immune responses following CHIKV infection was conducted to elucidate the involvement of gut microbiota in CHIKV pathogenesis. CHIKV joint inoculation induces gastrointestinal infection and histological damage, drives fluctuations in gut microbiota, markedly increasing the abundance of Bacteroides fragilis and Prevotella sp. and upregulates conjugates of taurine and bile acids. CHIKV infection further exacerbates systemic inflammatory burden and activates intestinal interferon (IFN) signaling cascades, which supports gut repair and mucosal regeneration, but low antiviral responses to CHIKV infection compared with that of adult animals. Our results suggest that the gastrointestinal tract, along with its microbes and metabolites, modulates CHIKV infection in an age-dependent manner, providing critical insights for diagnosis, treatment, and novel therapeutic development.

Intestinal microbes are closely related to vital host functions such as digestion and nutrient absorption, which play important roles in enhancing host adaptability. As a natural “laboratory”, caves provide an outstanding model for understanding the significance of gut microbes and feeding habits in the habitat adaptability of hosts. However, research on the relationship between gut microbes, feeding habits, and the adaptability of troglobites remains insufficient. In this study, we compared the characteristics of the intestinal microbes of Sinocyclocheilus cavefish and surface fish and further established the relationship between intestinal and habitat microbes. Furthermore, we conducted environmental DNA (eDNA) (metabarcoding) analysis of environmental samples to clarify the composition of potential food resources in the habitats of the Sinocyclocheilus cavefish and surface fish. Results showed that the structure of the Sinocyclocheilus gut microbes was more related to ecological type (habitat type) than phylogenetic relationships. While horizontal transfer of habitat microbes was a source of gut microbes, hosts also showed strong selection for inherent microbes as dominant microorganisms. Differences in the composition and structure of gut microbes, especially dominant microbes, may enhance the adaptability of the two Sinocyclocheilus fish types from the perspectives of food intake, nutrient utilization, and harmful substance metabolism, suggesting that food resources, predation patterns, intestinal flora, digestive and absorptive capacity, and feeding habits and preferences are linked to habitat adaptability. These results should facilitate our understanding of the significance of fish gut microbes to habitat adaptation and provide a new perspective for studying the adaptive mechanisms of cavefish.

Many studies have demonstrated the association between intestinal microbiota and joint diseases. The “gut-joint axis” also has potential roles in chikungunya virus (CHIKV) infection. Pro-inflammatory arthritis after CHIKV infection might disrupt host homeostasis and lead to dysbacteriosis. This study investigated the characteristics of fecal and gut microbiota, intestinal metabolites, and the changes in gene regulation of intestinal tissues after CHIKV infection using multi-omics analysis to explore the involvement of gut microbiota in the pathogenesis of CHIKV infection. CHIKV infection increases the systemic burden of inflammation in the GI system of infected animals. Moreover, infection-induced alterations in GI microbiota and metabolites may be indirectly involved in the modulation of GI and bone inflammation after CHIKV infection, including the modulation of inflammasomes and interleukin-17 inflammatory cytokine levels. Our results suggest that the GI tract and its microbes are involved in the modulation of CHIKV infection, which could serve as an indicator for the adjuvant treatment of CHIKV infection.